Bassett says there was a doubling of asthma cases between 1980 and 2004.

More Carbon Dioxide, More Flowering Plants

Researchers say the mechanism is fairly basic: there is more carbon dioxide in the air, which means more flowering plants, which means more sneezing and wheezing.

Plants, of course, thrive on carbon dioxide, just as animals and human beings thrive on oxygen. For people with asthma or allergies, though, it is too much of a good thing.

"What you see in an urban area is sort of a microcosm of the climate to come," said Lewis Ziska, a weed ecologist at the U.S. Department of Agriculture. "Plants are not as sexy as polar bears or penguins, but in terms of how they affect human society, they have a much greater impact."

Ziska pointed to a tree.

"Here's an oak tree that's seven or eight feet tall, and while its shade is certainly welcome in summertime, the amount of pollen it can produce is not during the springtime.

Scientists say that since average temperatures and carbon dioxide levels have been rising in the past few decades, that may help explain why the misery index has been going up, too. Other possible causes, such as new pollutants, are also being investigated.

Medicine is working to keep up with the increase in allergy cases. The newest allergy medications relieve symptoms without the drowziness typically caused by older remedies.

Environmental advocates also point out that the solutions that would reduce climate warming — reduction in the burning of fossil fuels which release carbon dioxide — would have the added benefit over time of lowering the pollen count.

And if you need more, "Sunglasses work great," said Bassett. "They reduce pollen in the eyes."